I read the other posts on this question, and none of the solutions work. It is occuring over a corporate network, with the security as WPA-Enterprise, the certificate is Equifax Secure Global eBuisness CA-1.No matter how many times the network properties are removed and re-added or the drivers for the wireless adapter are updated. Also, joined with this problem, on the same network is a problem on xp machines, where they switch the settings that are required for Open WEP instread of WPA, TKIP.This problem happens across a range of machine makes and only on Vista and XP.